Cooperative Ge-N bond activation in hydrogallation products of alkynyl(diethylamino)germanes (Et2N)nGe(C≡C tBu)4- n

Uhl W., Tannert J., Layh M., Hepp A., Grimme S., Risthaus T.

Abstract

Treatment of the alkynyl(diethylamino)germanes Et2NGe(C≡ CtBu)3 (1) and (Et2N)2Ge(C≡ CtBu)2 (2) with dialkylelement hydrides tBu2MH (M = Al, Ga) afforded in high yields the hydrometalation products (tBuC≡C)2(Et 2N)Ge[C(MtBu2)=C(H)tBu] (3), ( tBuC≡C)(Et2N)Ge[C(MtBu 2)=C(H)tBu]2 (4) and (tBuC≡C) (Et2N)2Ge[C(GatBu2)=C(H) tBu] (6). The Lewis acidic aluminum and gallium atoms showed a close contact to the nitrogen atoms of the amino groups attached to germanium, which resulted in relatively long Ge-N bonds and short Al-N or Ga-N distances. The structures of these molecules and the strengths of the interactions were investigated by dispersion-corrected density functional theory. This activation of the Ge-N bonds caused an unprecedented reactivity of compounds 4b and 6. 4b reacted with PhC≡CH under mild conditions and elimination of HNEt 2 to give the mixed dialkynyl compound (tBuC≡C) (PhC≡C)Ge[C(GatBu2)=C(H)tBu]2 (5), while facile insertion of RN=C=X into a Ge-N bond of 6 led to the formation of the six-membered Ge-C-Ga-X-C-N heterocycles 7 (R = Ph, Et; X = O, S). © 2013 American Chemical Society.